1. Field of the Invention
The present invention relates to a semiconductor integrated circuit device, and more particularly to a semiconductor integrated circuit device including a non-volatile semiconductor memory in which data are rewritable.
2. Description of the Related Art
A storage capacity of a non-volatile semiconductor memory in which data are rewritable, e.g., a NAND type flash memory tends to be further increased.
When miniaturization of a memory cell advances with an increase in storage capacity, there has emerged a phenomenon which has conventionally rarely appeared, e.g., a phenomenon such as a fluctuation in threshold value due to potentials of floating gates of cells adjacent to each other. This fluctuation in threshold value is called the proximity effect.
The proximity effect fluctuates a threshold value of a memory cell in which data has been already written. This becomes a problem when narrowing a threshold distribution width. In order to narrow the threshold distribution width, correcting a fluctuation in threshold value due to the proximity effect can suffice. As this correction technique, an improvement in data writing method has been sought. A known example of an improved data writing method, there is Jpn. Pat. Appln. KOKAI Publication No. 2005-243205.
However, the improved data writing method requires page flag data indicative of a current state of a page. Reading page flag data is an operation which is added to a writing sequence. Reading page flag data obstructs an increase in speed of a write operation.